Heretofore, for example, in the production of electronic circuit boards, a printing material, such as cream solder, has been used to solder electronic parts, such as chip parts, on a circuit board, and a cream solder printing device has been used to print or apply said cream solder in a desired pattern. Conventional printing of cream solder has been effected by using the following method and device. Referring to FIG. 4, the numeral 1 denotes a circuit board; 2 denotes a land to have cream solder 4 printed thereon; 3 denotes a solder resist; 5 denotes a screen mask of metal formed with openings 6 in a desired pattern; and 7 denotes a printing squeegee adapted to make a linear movement on the screen mask 5.
Cream solder printing comprises the steps of placing a screen mask 5 in position on a circuit board 1, feeding cream solder 4 onto the screen mask 5, linearly moving said squeegee 7 in contact with the screen mask 5 under a suitable printing pressure to fill the cream solder 4 into openings 6 in the screen mask 5, and separating the screen mask 5 from the circuit board 1, whereby the cream solder 4 is printed or applied on the circuit board 1 in a desired pattern through the screen mask 5.
In this connection, if the cream solder printing is continuously performed, the cream solder 4 moves around to the back of the screen mask 5 to adhere thereto as shown in FIG. 4 (b).
When such adhering cream solder 4 is transferred to the circuit board 1, it forms a cause of short circuit or the like. Therefore, usually the printing device is provided with a cleaning device 9 as shown in FIG. 5 so as to make it possible to remove the adhering cream solder 4. In this figure, the numeral 10 denotes a cleaning squeegee; 11 denotes a cleaning paper; 12 denotes a cleaning paper supply source; and 13 denotes a cleaning paper winding section. In addition, 8 denotes a frame.
The cleaning operation is performed as follows. First, the cleaning device 9 is moved in its entirety to the position A, where the cleaning squeegee 10 is then lifted until it comes in contact with the screen mask 5 through the cleaning paper 11. And with this state maintained, the cleaning device 9 is moved toward the position B. When the cleaning device 9 reaches the position B, the cleaning squeegee 10 is lowered, and the portion of the cleaning paper 11 which has been used for cleaning is wound by the cleaning paper winding section 13 while the cleaning paper 11 is fed from the cleaning paper supply source 12. Thereafter, the cleaning squeegee 10 is lifted again and moved toward the position A in the same manner as described above. When it reaches the position A, the cleaning squeegee 10 is lowered and the cleaning device 9 is returned to its original position to complete the cleaning.
Further, in recent years, in addition to the above arrangement, as shown in FIG. 6, there has been proposed an arrangement comprising a cleaning device 14 provided with an air sucking section 15 connected to an air suction mechanism 19. The numeral 17 denotes a supply source which supplies a cleaning paper 16 and 18 denotes a winding section therefor. In cleaning operation, the air sucking section 15 is moved to the position A and lifted until its front end contacts with the screen mask 5. With this state maintained, the air sucking section 15 is moved toward the position B along the screen mask 5 to remove the cream solder 4 adhering to the openings and the back of the screen mask 5. That is, the air sucking section 15 connected to the air suction mechanism 19 is held in contact with the screen mask 5 through the cleaning paper 16 which is air-permeable to the extent that air easily passes therethrough, while the cream solder 4 adhering to the openings 6 is recovered by the cleaning paper 16 through the suction of air. After the cream solder 4 adhering to the openings 6 has been removed in this manner, the suction of air by means of the air suction mechanism is brought to an end and the air sucking section 15 is lowered, whereupon the initial state is restored to complete the cleaning operation.
According to this printing device using air suction, the rate of removal of cream solder 4 can be increased as compared with the cleaning using the cleaning paper 11 alone.
However, even with said conventional printing device used, some amount of cream solder 4 remains on the screen mask 5, presenting a problem that such remnant results in disfigurement or blur on the print surface. Particularly, the physical properties of the cream solder 4 influence this problem such that if the cream solder 4 has high viscosity, it tends to remain.
The present invention solves the foregoing problem and has an object to provide a cleaning device and a cleaning method that eliminate the possibility of allowing a printing material such as cream solder to be left over on the screen mask.